1. Field of the Invention
The present invention relates to a polycarbonate and polysiloxane block copolymer, particularly a novel polycarbonate and polysiloxane block copolymer useful as an engineering thermoplastic resin, and a flame retardant resin composition containing the same.
2. Description of the Related Art
A copolymer having a polysiloxane block and a polycarbonate block, as disclosed in Patent Documents 1 and 2, can be obtained as a polycondensate from a dialkylpolysiloxane containing a phenolic hydroxyl group at both terminals, a bisphenol A and a carbonating agent. In fact, such a polycarbonate-based resin can provide excellent properties in low-temperature impact resistance and processability, but fails to provide sufficient flame retardance.
Meanwhile, Patent Documents 3 and 4 disclose methods for providing a flame-retardant polycarbonated copolymer comprising a brominated bisphenol A and a halogenated phenol. Nevertheless, these methods are undesirable due to the use of halides whose halogen, when combusted, is harmful to the environment and thus human health.
Furthermore, Patent Documents 5 to 7 disclose flame retardant polycarbonate resin compositions. In these methods, a phenyl group-containing hydrogenpolysiloxane is added to a thermoplastic polycarbonate resin to attain favorable flame retardance. Unfortunately, these methods involve such problems as the use of an expensive phenyl group-containing hydrogenpolysiloxane and unstable flame retardance resulting from a small amount thereof according to kneading conditions.